On domains added before version 1.6.0 using the Nginx webserver, Elementor editor may fail to load and log 400 errors.
This happens because of the try_files directive in the Nginx vhost template:
try_files $uri $uri/ /index.php$is_args?$args;
Fix:
To resolve this, edit the vhost file for the affected domain from Domains > Vhosts File Editor and update the directive to:
try_files $uri $uri/ /index.php?$args;
This will be automatically fixed in the 1.6.0 update for both existing and new domains.